Watch it with one eye open. First the left. Then the right. Or look at the opening of the tunnel. Then to the far right of the frame. Says a commenter at Geeks Are Sexy: “It’s actually timed in phase with the passing of the doors and windows. Since most of the train’s features are equidistant in regards to each other, the frame rate can be set to match the speed of the train, causing it to appear still. Here, the frame rate is twice the rate of the passing of the train, causing every other frame to return it to it’s apparent starting location. With the blur of motion, your brain is left trying to discern its direction, but since there is no 3D information to go on, you’re left bouncing between two possibilities.” He lost me at frame rate, but since the guy is staring at the tunnel opening, I’m going to say it’s coming out of the tunnel.
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